Variable condenser



Sept. 4, 192s. 1,683,558

F. A. KOLSTER VARIABLE CONDENSER Filed April 28, 1926 2 Sheets-Sheet l Z9 /15 I7 Z -llllllllll /NVETOH Frederick AKO/ferr f" @ff jjj ran/1ers sept 4, 192s. 1,683,558,

F. A. KOLSTER VARIABLE CONDENSER Filed April 28, 1926 2 Sheets-Sheet 2 N'NN LII

/g A Trafmfrs.

Patented Sept. 4,

:Banamex .l-x'onsfrnn, or' raro "ahrc, cnrronma. a

v "vamente coNnnNsma 4 I -appu'um'nied apra as, 192s'. sum No'. 105,050.

This invention. relates generally to a variable tuning device adapted to be used in conjunction with radio apparatus.

In radio receiving equipment it is customary to .employ a plurality of variable tuning condensers operated from a `unitary or gang control for simultaneously 'varying the electrical properties of two or more resonant circuits. For best results these resonant circuits 10 must be accurately tuned over a wide range of radio frequency. 'In manufacturing radio e uipment it is difficult to maintain theelectrlcal constants sufficiently close" to make it possible to 'employ a gang control condenser without making individual adjustment of the separate condensers. In the past such adjustments have been made by ex ensive coupling devices between the shafts o the various condensers'so that the rotary plates ofv one or more of the condensers mlght'be set at a different angular position from the others. These .prior devices were also diiiicult to incorporate in the ordinary panel type of radio set and electrical connections to the other instruments could not be readily made.

It is an object of this invention to devise a ang control condenser structure which may e readily adjusted to tune a radio set at maximum efiiciency throughout its wave-length range.

It is a further object of this invention to devise a gang condenser which may be readily incorporated with a standard radio receiving set.'

It is a further object of this invention to provide a novel form .of control for a tuning device.

It is a further object of this invention to devise a gang condenser structure which will have minimum electrical losses and will be ru ged in construction.

urther objects of this invention will appear from the following description in which I have set forth the preferred embodiment of my invention. It is to be understood that the scope of the invention is'only to be determined by the appended claims and the state of the prior art. v

'- Referring to the drawings: "Figure 1 is aside elevational'view of thedevice of this invention.

Fig.' 2 is a cross sect1onal view taken along the line 2-2 of Fig. 1.

.the line 34-3 of Fig. 1.

a Fig-3 is a cross sectional view taken along Fig. 4 is a detaily view showing for one of the condensers. 1g. 5 1s a circuit diagram showin the manner 1n which the device is connecte standard radio receiving set.

" The devlce includes generally. a metal the mounty 'p frame 10 which is adapted to be operatively v disposed behind an instrument anel 11 offa radio set. The frame 10 is ma e as ri 'd as v possible and comprises upper horizonta bars 12 and 112 and lower horizontal bars 13 and 113, these upper and lower bars bein interf connected by the vertical end mem ers 14y and the vertical Vintermediate members 15.

Cross bars 16 and 17 serve to make the frame more rigid. Within the frame 10 there is arranged a horizontal shaft 18 which is preferably ]ournaled in bearings 19 provided upon the vertical members or webs 14: and 15. A plurality of variable condenser structures 20, l21, 22 and 23 are operatively mounted in spaced relationship withinthe frame 10 so as to be simultaneously varied upon rotation of the shaft 18.

A suitable form of variable condenserI structure is shown in Fi s. 2 and 4 and comprises a group of space rotor plates 24 div rectly mounted-upon the shaft 18. The rotor plates are adapted to interleave a group of spaced stator plates 25 which are suitably mounted upon the insulating .strip 26. One suitable form of mounting comprises a. bracket 27 secured to the stator plates 25 and tothe insulating strip 26 by means of bolts 28.' The ends of the insulatin strip 26 are secured to the rear faces of the ars'12 and 13 by suitable means such as lscrews 29, the apertures 30 provided in the insulating strip for reception of these screws 29 bein enlarged so as to permit lateral adjustment o the insulating strip.

To indicate the angular position `of the shaft 18 there is provided an indicating dial 'or drum 31 which is mounted upon this shaft, preferably between the intermediate vertical members 15. This indicating dial is adapted to be visible through an aperture 32 in the instrument panel 11 and is provided with Y los there is provided a control haft 34 which is rotatably mounted below the drum 31 and in alinement with the same so as to roject out thru the anel 11. The mounting or the control sha t l34 includes a plurality of journal" part of the frame and serves to bridge the The pulley1 space occupied by the lower portion of vthe drum 31.F0

To pre'vide means for operatively connecting the'A control shaft 34 with the shaft 18 plates may be made to any one of the screws 28. Metal shields 61 may be positioned between the condensers and grounded to the frame in order to reduce interca acitative coupling. The front bars 112 an 113 may be employed. for. opera-tively mounting the device behind the instrument panel 11, and as shown, are lsecured to a metalpanel 35.

The manner 1n which the device of this invention isassociated with a radio set is shown in lig. 5. .In this instance it has been Shown as incorporated with a. radio receiving cirthere is also mounted upon the latter shaft `a\\cuit comprising radio eiliciency'vacuum tube pulley wheel 39 adapted to cooperate with a small pulley wheel 40 fixed to the shaft 34. wheel 39 is preferably'formed of two split alves 41 and 42'as shown in Fig. 3, these halves being secured to onev face of the drum 31 as by means of screws 43.

Trained about the pulley wheels 39 and 4( there isa flexible belt or cord 44, a pair of idler pulleys 45 Aand 46 being provided to track the cord 44 upon the pulley wheels 39 and 40. A suitable form of tensioning device 25 for the cord 44 is shown in Fig. 3 and comprises a pair of resilient lingers 47 mounted within slots 48 in the pulley wheel portion- 41, the resilient ends of these fingers being disposed within a slot 49 openi-ng into the periphery of the pulley 39. The ends 50 of the cord 44 are secured to the ends of the fingers 47'so as to be constantly urged in a direction to tension the cord. Thus upon rotation of the control shaft 34the shaft 18 will be rotated to simultaneously vary the respectivecapacitances of the condensers 20 to 23 1n-V clusive.

In assembling condensers such as described above it has'been found that the-respective minimum capacitance of the different vcondenser structures will vary between certain limits. In order to definitely fix thiscminimum capacitance each condenser structure is provided with va small adjustable condenser 52 which is mounted upon the lrear face of the insulating strip 26. In the construction shown this variable condenser comprises a metallic stri 53 which is connected to a screw 54 which is threaded intothe bar 12,

thus being grounded to the frame. The strip 53 forms one electrode of a condenser While the spring strip 55 forms the other electrode, the lower end of this strip' being connected with two of the bolts 28.' The overlapping portions of the strips 53 and 55 are separated by means of a strip 56 and a screw 57 serves to press down the 'upper plate against the lower a more or less amount depending upon the'capacitance desired.

For making connections to the rotor plates of the respective condenser structures there v are provide-- terminal connectors 59 which are connecte` to the stator plates by'means of a iiexible ribbon or other suitable conductor 60. Connections to the insulated stator amplifiers 1, 2 and 3 and a detector tube 4. These vacuum tubes may be of the usual three element type comprising a grid 5, filament or electron emission element 6 and plate 7 The grid circuit for the tube 1 is provided with an inductance 62 `for coupling two antennae-63 and ground 64. Inductive cou ling devices 65, 66 and 67 are also provi ed for coupling together the tubes 1, 2,13 and' 4 in cascade as shown. The condenser structures 20, .21, 22 and 234` are connected respectively across theinductance 62 and the coupling devices 65,- 66 and 67, so as to selectively tunev the entire system to a certain frequency. .It is ofcourse obvious that `the system may be energized by A and B batteries 68 and 69 respectively, while the grids of the ampliertubes may be maintained at a ne ative potential' bythe'use-of a B battery O. The output of the detector tube 4l has been shown as supplying a translator 71 which may consist of atelephone or any further 1" system of audio frequency amplifiers. By employing the small adjustable condensers '52 in shunt with the variable condensers the minimum capacitances of the respective Variable condensers ma be made equal so as to 1N facilitate ma-intainlng the system in resonance to a single frequency vthroughout its frequency range.

In addition to providing a structure which is rugged and has a high electrical efficiency Il. it may be readily assembled and adjusted to operate a receiving setat maximum eliciency. Thus if in the process of manufacture one of the coupling devices has an inductance which x .is lower `than Ithe other, then the'positionof 1l the insulating strip 26 of its associated condenser may be adjusted by loosening the screws 29 to positionthe stator plates 25 so i as to slightly increase its maximum`capacitance.l Dielectric lossesy are reduced to a minimum since the 'stator plates 25 are. spaced a considerable distance from .the insulating strip 2 6 and aremerely. supported from two points represented by the brackets 27. x

1. A device of the class describedv comprising a frame adapted-to be'mounted behind an instrument panel, a plurality ofvariable condenser structures mounted on said |30 tures having rotor elements mounted on said:

frame, a horizontal shaft parallel to the panel connecting said structures, said frame including va plurality of metallic shielding fplates intermediate said l condenser structures on lmore than two sides thereof a control shafty extending normal to said former shaft, and means v:for operatively connecting said Shafts. 2. A device of the class described com rising a frame adapted toibe mounted be ind an instrument anel, a horizontal shaft journaled. to said rame and extending parallel to'said panel, a plurality of condenser strucshaft, an indicating dial: mounted on said shaft betweenl two of said condenser struc-v tures and visible thru an aperture in said panel, a control shaft extending thru' said panel, and means for'operatively connecting said control shaft and first named shaft.

3. A device of the class described comprising a metal frame, a shaftjournaled to said frame and grounded tothe same, a plurality of lcondenser structures mounted on said frame, said structures each includin a rotary element mounted on said shaft, an a stator element mounted on said frame,'the

mounting for the stator element including an insulatin str ip secured at its ends to said frame and orming a cantilever support forA said stator intermediate one side thereof whereby the said statorlates are suspended from a single side thereo leaving the remaining sides free froml connection with said frame.

.4. A device of the class described comprising a metal frame, a shaft journaled to said frame and grounded to the same, a plurality of condenser structures mounted on said frame,said structures each including a rotary element mounted on said shaft, and a stator element mounted on said frame, each of said elements consisting'of plate members in arallel spaced relationship', an insulating strip ad'ustably secured at its ends to said.

frame a jacent each of said rotary elements, said strip lforming a cantilever `support at its intermediate portion for said stator -element, means whereby said strip may be adjusted laterally, in position on 'said frame for centering the plate members of said stator element between the plate members of said rotor element'said stator element being wholly suspended from a single side thereof leavin the remaining sides free from connection with said frame 5. A device of the class described comprising a frame having spaced uppei` and lower horizontal lframe bars, a shaft journaled in said frame between said bars and. drum ends f the bars, a rotatable control shaft journaled beneath said indicating drum, the mounting for said control shaft being secured to said. lower bars, means for operatively connectin the control shaft .and said first mentions shaft, a plurality ofl variable condenser v structures mountedon said frame on either side ef said drum, said condenser structures each including a rotor mounted on said shaft and a stator mounted on said frame. 6. A device of the class described comprisrmg'a frame having spaced upper and lower .horizontal frame bars, a shaft journaled in sa1d frame between said". bars and parallel tov the same, anV indicating drum' mounted upon said. shaft -intermediate theends of the bars a ,rotatable control shaft jouriialed beneat saidfindicatin'g drum, the mounting for said c ontrol shaft including a U-shaped portion interconnecting 'intermediate portions of said'f lower frame bars, means for operatively connectinglthe control shaft and said first mentioned s aft, a plurality of variable condenser structures vnio ted on said frame on either side of said um, saidpcondenser structures each includin a rotor mounted on said shaft and an ins ated stator mounted on said frame,

7. multiple variable condenser system comprising a chassis substantially in the form of a box-like frame divided into two portions,

a rotatable shaft journaled in the ends of said chassis and 'passing longitudinally through both portions of said box-like frame, a plurality of insulated'panel members secured to one side of said chassis, a plurality of variable condenser units each including sets of stator and rotor lates disposed in both portions of said box'- e frame with the rotor plates thereof carried by said rotatable shaft, the stator plates thereof being supported from one side of said box-like frame on said insulated panel members, and means disposed between the said portions of said box-like frame for `controlling the .movement of said rotor plates. v

8. A multiple variable condenser comprising aemetal frame provided with shielding means adapted to be mounted vbehind an instrument panel, said frame having a plurality of compartments, a variable condenser structure disposed in each compartment, a shaft 4arranged parallel to ythe instrument panel and connecting said structure, a control .shaft extending through said panel, means for operatively connecting said control shaft andl said first named shaft and additional shielding means disposed parallel to said shaft and intermediate said aforementioned shielding means and adapted to shield each of said condenser structures from disturbancesarising outside of said metal frame.

9. A multiple condenser structure comprising a plurality of condensers, an instrument panel, a common voperating shaft for said condensers, and means for supporting the shaft in a position parallel tothe plane of the panel comprising a plurality of metal plates in some of which said shaft is journale-d, whereby said condensers are electrostatically shielded from each other, and meansv for controlling the rotation` of said shaft from the front of said panel. l Y

10. A multiple condenser structure e0m-v prising a pluralityA of condensers, an instrument panel,.a common operating shaft. for said condensers, and means for supporting the shaft in a position parallel to the plane of the panel comprisinga plurality of metal plates 'disposed at the ends of the condenser structure and intermediate the condenser-s, said shaft being journalled in the plates located at the ends of the condenser structure,

whereby said condensers are electrostatieally shielded from each other.

11. A multiple variable ycondenser structure eomp'risinga panel, a plurality 0f variable condensers, an actuating shaft for operating all of said condensers simultaneously,

and integrally connected means extendingl normally of the paneland rearwardly there,- rom and engaging said shaft, to maintain said shaft in a position parallel to the plane of the panel.

In testimony whereof, I have hereunto set my hand. .i

FREDERICK A; KOLSTER. 

